Generally, a wireless communication system including a base station (BS) and a user equipment (UE) broadly provides various types of communication services including voice, data and the like to user devices through one or more base stations. And, a single base station may cover at least one or more cells.
In recent years, user equipment traffic has exploded due to the development of the wireless communication system. To handle the explosion of the user equipment traffic, the structure of the current wireless communication system has been changed from the conventional vertical structure corresponding to a centralized based station based on a macro base station or a macro cell into a structure in which various kinds of small cells such as a pico cell, a femto cell and the like are interconnected to the macro base station or the macro cell.
In small cell enhancements for E-UTRA and E-UTRAN as one of 3rd generation partnership project (3GPP) standard scopes, a lot of discussion has been made on improvement of a scenario using low-power base stations such as a pico base station and a femto base station and a concept of dual connectivity for enabling a user equipment to connect with the macro cell and the small cell simultaneously.
Particularly, a small cell deployment scenario and requirements have been specified in TR 36.932. Moreover, additional functions and potential high layer technologies for improving the performance of E-UTRA and E-UTRAN and meeting the small cell deployment scenario and the requirements have been discussed in TR 36.842.
Meanwhile, the small cell as the low-power base station, for example, the pico or femto base station may receive a service request from the user equipment connected to the pico or femto base station and then provide corresponding service. However, in some cases, the pico or femto base station may not provide the service requested by the user equipment appropriately. Moreover, in this case, since the user equipment is not connected to the macro base station although it is connected to the pico or femto base station, the macro base station may not provide the service in place of the pico or femto base station. In particular, it may cause a problem that the user equipment connected to the small cell is unable to receive the service as much as it requests. Accordingly, a method of solving the above problem is required.